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• Samples from Well 17W, located downgradient of the central portion of the south mining area, display a Na-HC03 type water with an average TDS value of 625 mg/l for 1993. This value is both lower than the baseline average of 906 mg/l and the baseline range of 628 to 1,662 mg/l. Samples from Vell 18W, located at the south end of the south mining area, display a NaMgC a-HC03 type water with en average TDS value of 625 mg/l for 1993. This value is both lower than the baseline average of 669 mg/l and the baseline range of 626 to 778 mg/l. Comparison of Ground Voter Quality to Voter Use Standards. The Colorado Department of Health (CDOH) drafted basic standards for ground water, including standards for agricultural use (i.e., irrigation and livestock), in 1986 (CDOH, 1986). These standards have been summarized and are presented as Table 8 in Appendix A. Parameters denoted with an asterisk on this table pertain to livestock standards; alt other parameters pertain to irrigation standards. Results of analyses performed on samples obtained from monitoring wells during the 1993 water year have been compared to these standards, and the comparison results are presented in Table 9 (Appendix A). • Table 9 shows that alluvial Vells bA2, 7A2, 19A, 21A, 23A, and USGS A8; overburden Vell 140V, and coal Vell 16W all exceed the irrigation dissolved manganese standard of 0.2 mg/l. This standard applies to crops grown in soils with pH values loner than 6.0. In soils with a higher pH (as is found in the agricultural soils surrounding Seneca II-W Mine), a more realistic standard would be 10 mg/l (EPA, 1976). The irrigation dissolved iron standard of 5.0 mg/l was exceeded at alluvial Vells 7A2 and 23A and overburden Vell 140V. Voter with this iron concentration will precipitate iron oxides on the leaves when the crop is spray-irri gated, bui should not be a problem for flood irrigation (EPA, 1976). Boron concentrations at overburden Vell 140V exceeded the standard of 750 ug/L. This boron standard applies to the irrigation of primarily fruit, nut, and citrus trees. For crops not listed by the CDOH (none of which grow in this area), the appLicabLe standard is 5,000 ug/I. • Fluoride values at overburden Vell 180V and alluvial Vell 22A exceed [he standard of 2 mg/l. High fluoride values have also been noted at the Seneca II Mine in certain wells with a high percentage of sodium (as is also the case with Vell 150V). This observation 7